Fuel Cells (FC's) are electrochemical devices that directly convert the chemical energy of a fuel into electricity. In contrast to energy storage batteries, fuel cells operate continuously as long as they are provided with reactant gases. In the case of hydrogen/oxygen fuel cells such as proton exchange membrane fuel cells, which are the focus of most research activities today, the only by-product is water and heat if pure hydrogen is used. The high efficiency of fuel cells and the prospects of generating electricity without pollution have made them a serious candidate to power the next generation of vehicles, houses and mobile devices. More recently, focus of fuel cell development has extended to remote power supply and applications, in which the current battery technology reduces availability because of high recharging times compared to a short period of power supply (e.g. cellular phones).
There are basically three major applications of fuel cells, namely, transportation, stationary and portable powers. In the case of transportation applications, pure hydrogen appears to be the most desirable fuel rather than on-board hydrogen production from hydrocarbon fuels, given the factors such as complexity, cost and slow start-up. This suggests that a fuel cell power system without fuel processing is most appropriate for transportation applications. In the case of stationary applications, especially in the low power range (<10 kW), two types of application, i.e. residential and backup power (or uninterruptible power units) are typical, with the former being generally installed with both a fuel processor and a fuel cell power system, and the latter only a fuel cell power system. Depending on the applications, fuel cell manufacturers have been putting their resources on either transportation, residential or backup. The products developed and manufactured in such cases cannot be transferable, i.e. each product requires a separate, lengthy and costly process of development, manufacturing and assembly.
Still, one of the most important issues impeding the commercialization of fuel cells is the cost. Besides the material, the complexity in the present designs shares a significant portion of the high cost. As it is well known in the field, a fuel cell power plant commonly comprises of hundreds (if not thousands) of components, with all of these components being properly connected, integrated, and housed in a chamber. It is a common feature that these multiple components have been made to best utilize the space inside the chamber in order to make the fuel cell system more compact. However, this feature has led to poor manufacturability, poor accessibility for assembling and poor serviceability. It is often the case that the whole system or subsystem (such as fuel processor, fuel cell stack) must be replaced even though there is only one part that has actually failed.